a. Field of the Invention
This invention relates to methods for producing bicomponent acrylic filaments.
b. Description of the Prior Art
It is known to form bicomponent acrylic filaments by assembling alternating layers of two different spin dopes in a tube and then feeding the assembled layers to a conventional spinnerette to form filaments. The spinnerette has a larger cross-sectional area than the tube through which the layers are fed and, to expande the cross-sectional area of the assembly of layers to the cross-sectional area of the spinnerette, the spinnerette is connected to the tube by a short tube having a conical configuration. When a relatively small spinnerette is used, the interfaces between adjacent layers of the spin dope retain their integrity to a degree such that bicomponent filaments are formed, a bicomponent filament being formed at each point where an interface between two adjacent layers intersects a hole in the spinnerette.
It has been found that this method is unacceptable where a fairly large spinnerette is used. The conical tube connected between the feed tube and the spinnerette expands the cross-sectional area of the stream in such a manner that the layers become sufficiently mixed at the interfaces that good bicomponent fibers cannot be formed.
It has been found that little or no mixing of adjacent layers at the interface therebetween will occur when the transition tube between the feed tube and the spinnerette has a parabolic configuration.